Known stabiliser units, which are so-called dynamic track stabilisers, are currently vibration units which are equipped with a mechanical vibration drive comprising two eccentric masses rotating in opposite directions. The two rotating eccentric masses are coupled to each other via gearwheels in such a way that diametrically opposed rotation of the masses about the associated axes is ensured. The vibratory force components in the vertical direction cancel each other out with this arrangement and the vibratory force components are amplified in the horizontal direction, i.e. in a plane parallel to the track transversely to the longitudinal direction of the track. Heaps of rock such as railway ballast in particular can be compacted efficiently especially by action of horizontal vibrations, especially when the frequency is chosen in such a way that the ballast assumes an elastic-liquid behaviour, which is the case at frequencies greater than 30 Hertz. Dynamic track stabiliser units are used for compensating irregular initial settings of the track on the ballast bed by purposeful controlled anticipation in that they are removed right from the start. This substantially increases the lifespan of the geometric track position. It is also known in this context to install two eccentric vibration units together in a stabiliser unit which are arranged in succession in the longitudinal direction of the track, wherein both vibration units are then usually coupled via a crankshaft, so that they run in synchronicity with respect to frequency and phase. In order to prevent the stabiliser unit from freely slipping on the rail and thus optionally causing chatter marks or excessive wear and tear on the rails, it is necessary to support the units statically via hydraulic cylinders against the machine frame and to additionally provide clamping rollers in addition to the flanged wheels which keep the stabiliser unit in a virtually play-free manner on the track.
For the purpose of controlling the energy introduced into the substructure of the track, it is known to arrange the rotating eccentric masses in an adjustable manner, wherein a displacement of the eccentric mass to the outside with static frequency causes an increase in the dynamically acting forces. There are also measuring devices which indicate a deviation from a given target subsidence of the track in the longitudinal direction of the ballast bed. Similarly, measuring devices for measuring the transverse inclination in the height using inclinometers or physical pendulums for example are used. A continuous dynamic transverse displacement resistance measuring device is also known, which measuring device is based on the principle of measuring the hydraulic drive power of the mechanical vibration unit and equalisation with the friction loss of the track on the ballast. The friction loss can be calculated by measuring the load as a normal force and the frictional value of the sleeper on the ballast, which is also known as resistance to lateral displacement. The displacement resistance is thus not measured directly but indirectly. The resistance to lateral displacement is the relevant quantity critical to security for the safety against buckling of a continuously welded track. The resistance to lateral displacement is usually determined at 2 mm of displacement path. The typical vibration amplitudes of the track in the case of dynamic track stabilisers lie at approximately 2 to 3 mm. The resistance to lateral displacement is one of the important quantities critical to safety in the construction of tracks and is mostly determined by complex measurement of individual sleepers usually under undesirable track blocking.
The vertical stiffness of the track is determined by measuring the force which needs to be applied for a specific subsidence of the track. Measuring devices provided for this purpose are based on the principle of applying a static load, mostly using hydraulic cylinders which act on the railway wheel sets. The value of the force by subsidence then leads to a vertical stiffness, which is an important measure for evaluating the quality of the track and the behaviour of the track under repeatedly occurring train loads. Strongly fluctuating track stiffnesses lead to irregular cases of subsidence under train loads and thus to respective errors in the track geometry. Since the vertical stiffnesses are strongly non-linear, the statically measured vertical stiffness is only significant within limits.
Accordingly, it would be desirable to provide an apparatus of the kind mentioned above which has a simpler and more compact configuration and allows an especially effective stabilisation of a track on a ballast bed. The resistance to the lateral displacement and the vertical stiffness of a track shall be measured in the simplest possible way in accordance with a further development of the system described herein. Furthermore, introduction of resonant frequencies into a track shall be avoided and the time intervals for an introduction of the resonant frequency shall be kept as short as possible.